Optical wave-guide cable networks are superior to the conventional communication networks based on copper, particularly with regard to transmission rates and transmission quality. Efforts are therefore being made to extend the optical wave-guide infrastructure for local, regional and long-distance communication connections. Efforts are also being made to integrate optical wave-guides gradually into existing copper telecommunication networks and to supply broad-band cable networks for the cable television service. A substantially broad-band supply and with it a forward-looking strengthening of the broad-band cable network for the provision of additional, new services, as well as the integration of energy-supply networks used for communications technology in communication networks is also economically desirable.
In order to extend the optical wave-guide cable network, at the moment, roads, footpaths, and other areas are dug up in order to lay the cables either directly or in so-called cable ducts. However, laying in this manner is very time-consuming and expensive and is only possible in frost-free ground.
In order to avoid digging works, so-called overhead cables can also be installed. This technique is used particularly for electrical power-supply in the long-distance communications range. In local and regional networks, however, owing to various disadvantages, overhead cables are now hardly used for supplying subscribers.
A cable-laying method has also recently been tried, in which a channel is cut in the road or footpath, the optical wave-guide cable is then put in place and the opening is filled with a filling material. The mechanical damage to the road or to the footpath is indeed considerably less than with cable-laying by excavation, but a lasting impairment or deterioration of the highways is also caused in this case.
In DE-A-42 03 718 it is proposed to lay the optical wave-guide cable in accessible water conduits, particularly storm sewers and to provide junctions to other cable-network sections on the manhole covers or on the walls of gullies or manholes. Digging works are necessary for connection to other networks.
A fixing element by which glass-fibre cables can be secured in sewers is known from JP-A-5 272 664. This known fixing element is prestressed so as to be approximately horseshoe-shaped prior to mounting in the sewer and is held in this shape by a connecting rod. The fixing element is connected to the cable and put in place in the sewer. As soon as all fixing devices have been put in place along the entire length in the sewer, the respective connecting rods, which are connected to one another by means of a wire, are pulled out and the fixing element presses itself against the sewer wall. This method of laying cables in sewers has the disadvantage, however, that, during the pulling-out of the rods, the fixing elements may slip and an optimal arrangement of the cable, for example, on the upper side of the sewer, is thus no longer assured. Moreover, this type of cable mounting is comparatively expensive.